Abstract: The fatigue and wear characteristics of Cr4Mo4V steel under lubrication of 4050 lubricant were evaluated.Tests were conducted using a rolling contact fatigue(RCF)test rig of the ball-on-rod type with 0.18 slide-to-roll ratio. S-N data showed continuous gradual decline and large dispersion. Rolling contact wear of Cr4Mo4V steel involved mainly abrasive wear, adhesive wear and fatigue wear. Wear volume became larger when time and stress increased. The maximum depth of raceway groove reached up to 17 μm. The rolling contact fatigue mechanism analysis of steel with different stress was investigated in detail by observing fatigue cracks of the junction of cross section and wear surface of rod specimens using optical microscopy and scanning electronic microscopy. It is found that there were two kinds of flaking, i.e. surface originated flaking (SOF) and white etching area originated flaking (WSF). The initial etching clearly reveals the RCF affected plastically deformed area at the edges of the test track of Cr4Mo4V steel rod material. With increasing contact cycles and contact stress, dark etching regions (DER), white etching area (WEA) and butterfly wings (WB) formed in the subsurface in sequence. Carbide peeling pits, adhesive wear and fatigue wear pits caused surface originated flaking. Carbides and inclusions in WEA and BW led to the generation of micro-cracks. Cracks extended deeper due to the presence of chain-carbide.